Recent results obtained from psychophysical experiment on humans and from molecular genetic experiments on human genomic DNA provide new insights into the relationships between the cone pigment genes, cone photopigments, and both normal and defective color vision. These results challenge several long-held ideas about the genetic basis of color vision and the photopigment basis of normal and defective color vision. The research provided here seeks to verify some of these new findings, offers a series of experiments to resolve some of the present ambiguities, and proposes tests of new hypotheses about the mechanisms for human color vision. The specific aims include: (a) further study of the characteristics of polymorphism of color vision among humans having normal color vision:; (b) an examination of the genetic basis of this polymorphism; (c) experiments to determine the nature of variation in the spectral mechanisms that account for dichromatic color vision; (d) an attempt to elucidate the relationship between X-chromosome photopigment genes and various types of defective color vision. Three techniques will be employed: (1) psychophysical tests of normal and color defective individuals, (2) examination of genomic Southern blots of DNA from subjects whose color vision has been carefully studied, (3) analysis of a retinal gross potential, the electroretinogram.